The present invention relates to methods and apparatus for protecting vascular structures during surgical procedures, such as during revision surgery to the spine.
Various surgical procedures to access to the anterior spinal column have been developed over the last few decades. Such procedures have permitted surgeons to perform repair and corrective surgeries on various parts of the spinal column, such as repairing the motion segments of the spine. The repair procedures include arthrodesis (using allograft bone, threaded fusion cages, impaction cages, as well as plate fixation), and spine arthroplasty (using artificial intervertebral discs for replacing a part or all of a removed disc, such as elastomer discs, metal on metal discs, metal-poly discs, pure ceramic discs, ceramic metal or poly discs, ball and socket discs, mechanical spring discs and hybrid discs, hydrophilic nucleus replacement, ballon polymer nucleus replacements, carbon fiber nucleus replacement)
The traditional surgical approach, for example, to a site in the anterior lumbar region the spine entails; an transperitoneal or retroperitoneal, anterior abdominal approach by means of an incision through, fascia and through or around muscle planes. Exposure of the affected spinal site also involves mobilization of the great vessels that lay immediately in front (anterior) of the lumbar spine. For example: removal of a degenerative disc and replacement with fusion cage or prosthesis requires mobilization of the vessels for exposure of the discs. The vessels are then allowed to return to their original position after the spinal procedure. Depending on the anatomical location of the surgical site, scar tissue may adhere to the aorta, vena cava and/or other retroperitoneal structures.
Normally postoperative scar tissue adheres to the vessels surrounding peri-spinal and spinal tissue obscuring the vessels as well as key anatomical landmarks. Due to the lack of the anatomical landmarks this scar often produces a nearly blind navigational field. The resultant scar tissue may become significantly problematic during any revision surgeries. While any surgery of the anterior spine requires, as a primary effort, great care in identifying key anatomical landmarks, anterior revision surgery requires navigation (often blindly) through varying degrees of tenacious scar bed. Identifying vascular structures and other key landmarks to safely commence the revision surgery poses a significant risk to injuring sensitive structures, particularly the vascular anatomy, which can cause severe problems and even death.
The vascular structures most at risk during surgery, particularly where revision surgery is involved, are the large veins that lie in front of the spine (e.g., at L1-L4: Vena Cava; and/or at L4-S1: Left and Right Iliac Veins). This is so because veins are relatively flat and thin-walled, making them more susceptible to injury during the surgical procedure. In some instances, the evidence of a venous injury during a surgical procedure may be delayed due to vessel tamponade during retraction. This injury may cause a patient to lose their entire blood supply within minutes. Arteries are also at risk during revision surgical procedures.
An existing publication, U.S. Patent Publication No. 2005/0177155, purports to address the issue of vessel protection during revision surgery. The '155 publication discloses the use of a plastic material for application over an annular spinal defect to minimize the amount of scar tissue in the area and to facilitate revision surgery. More particularly, a shield is configured for implantation over an anterior portion of the spinal column, where the shield includes a sheet of material having first and second adjacent portions in the shape of a “T”. The shield is placed over a spinal surgical site on an anterior spinal location between a spinal disk space and adjacent blood vessels. Assuming, arguendo, that the disclosure of the '155 publication enables the use of a shield to protect blood vessels, it does not address the issue of guiding a surgeon through, for example, varying degrees of scar bed and identifying vascular structures and other key landmarks to safely commence the revision surgery.
As revision surgery is likely to be required for a statistically significant number of patients receiving anterior spinal surgery, and as such surgery is potentially life-threatening to a patient, there are needs in the art for new methods and apparatus for protecting vascular structures during surgical procedures, particularly revision anterior surgery to the spine. This is particularly true with artificial disc replacement which when compared to other surgical prosthesis, such as total hip and knee replacements, rarely last longer than 15-20 years. Current evidence indicates that spine arthroplasties will improve that statistic. It is also well appreciated that spine arthroplasties may have a much earlier revision rate than their lower extremity counterparts.